diff --git a/Documentation/devicetree/bindings/serial/cdns,uart.yaml b/Documentation/devicetree/bindings/serial/cdns,uart.yaml
index e35ad1109efc..2129247d7c81 100644
--- a/Documentation/devicetree/bindings/serial/cdns,uart.yaml
+++ b/Documentation/devicetree/bindings/serial/cdns,uart.yaml
@@ -55,6 +55,7 @@ required:
 
 allOf:
   - $ref: serial.yaml#
+  - $ref: rs485.yaml#
   - if:
       properties:
         compatible: